Jason Lee begins a guest arc on
"Up All Night" Wednesday (Nov. 9), playing a down-to-earth single dad who has a spark with Ava.

Wait. Ava?

It's true --
Maya Rudolph's character will, in spite of her usual taste in men, find herself attracted to Kevin, who is Chris and Reagan's (
Will Arnett and
Christina Applegate) neighbor. Lee says Kevin brings out a different side of Ava than what we've seen of her previously.

"I think Ava is very likable, sweet, innocent, and ... he brings that out in her. And I like that she's not afraid to be that way around this guy," Lee says. "She's still very kind of smart-assy and jokey when they're around other people and whatnot, and it's all fun and endearing. But I think it brings out a cool side of her, and it certainly allows me to do something a little different, which is very cool.

"[I get to] kind of play it a little straighter and be a little bit more, I guess you could say leading man -- whatever the term is -- or just kind of 'the guy,' which I never really do, coming from [
'My Name Is Earl'] and things like that."

Lee has filmed three episodes so far, and he says there was no problem getting comfortable with the regular cast.

"Fortunately, they're all very cool people, and as a guest star, you hope for that because you want to be able to just blend right in and have fun and have it feel comfortable," he says. "And certainly, great show regulars help that immensely. ... And with Maya, I think there's great chemistry there. She is very playful. Everybody's just been totally inviting. There's a lot of improv and goofing off. I feel right at home, and so I thank them immensely for making it comfortable for me."

"Up All Night" has, like much of NBC's lineup, scuffled in the ratings some this season. The network has picked up the show's back nine episodes, though, and creatively it seems to have found a pretty good groove. It has a fan in Lee, who likes the fact that the show isn't just about scoring laughs.

"It's got heart. It's accessible. It's not better than thou," Lee says. "You know, it doesn't have that sort of comedy undertone to it. ... At the end of the day, you ultimately kind of relate to the people [in it].

"There's a sweetness to it too, which I think is very cool. ... It's a well-rounded show. It's believable and very cool in that way. And so I think that's a big part of the appeal for me, is that it feels like a well-rounded, real show. It's not just funny, you know?"

"Up All Night" airs at 8 p.m. ET Wednesday on NBC. Take a look at Ava and Kevin's first meeting: